In 2007, the United States federal laws implemented and required most passenger vehicles to include a tire pressure monitoring system (TPMS) to monitor and alert drivers of low tire pressure which degrades vehicle efficiency and performance. Continued use of a tire with low tire pressure can cause premature wear of the tire and in the worst case, catastrophic tire failure.
One TPMS system is Direct TPMS. In direct TPMS, a tire sensor is installed in the wheel, often the valve stem of pneumatic vehicle tire. These sensors are capable of monitoring several conditions of the tire including: tire air pressure, tire temperature, wheel rotation speed and other conditions. The sensors themselves include a specific sensor identification code (ID) and are capable of receiving electronic signals and sending electronic signals wirelessly from inside the wheel to an electronic control unit or module (ECU) in the vehicle which typically is connected to alert signals in the instrument panel in the interior of the passenger compartment. If a wheel sensor signals a tire pressure or other condition in a tire that is above or below a predetermined level, the sensor transmits a signal that is received by the ECU and an audio/visual indication is triggered to alert the driver to the condition.
Typical tire sensors used with TPMS systems are mounted on the valve stem, strapped on the rim or they could also be mounted against the tire wall. The electronic module generally includes a small battery, a circuit board with communication antennas or coils (receive and transmit), an air pressure sensor, a temperature sensor, a rotation detection device or accelerometer, a programmable controller and a memory for storing the sensor specific ID and other information depending on the TPMS system and capabilities. Modules that do not include a battery are under development. Due to the installation inside the tire or valve stem, sensors are designed to be permanently installed within the tire. Due to the finite life of batteries, power consumption is purposely low and the sensors are initially placed in a “sleep” mode so as to not use power until the vehicle or individual wheel is installed or sold to an end user. During operation of the vehicle in the field, it is common for the sensors to not be active or continuously reporting information to the vehicle ECU, but rather to perform tire condition checks at predetermined intervals to conserve battery life. When activated, the sensors emit a signal or signals which are received and interpreted by the ECU and processed according to preprogrammed instructions.
As TPMS systems advance in capability and increased safety options are included by the vehicle original equipment manufacturers (OEMs), vehicles are capable of identifying or alerting of the specific tire that, for example, may have low tire pressure. These systems accomplish this through the vehicle ECU being initially programmed or calibrated to recognize each of the specific wheel sensors associated with a particular position on the vehicle, for example, driver front or rear and passenger front or rear. When a new vehicle is manufactured, this initial programming or calibration may take place in the vehicle assembly plant or at a later time before the vehicle is purchased or delivered to the end user.
When, for example, the tires on the vehicle are “rotated” and their positions on the vehicle change as part of routine maintenance for longevity of tire life, it is important for the proper operation of the TPMS that the vehicle ECU be reprogrammed or calibrated to take into account that the prior position of the tires, and associated tire sensors, has changed.
TPMS tools have been developed which can wirelessly identify the specific sensor ID in the particular tires and transmit electronic signals to the vehicle ECU to update or retrain (reprogram) the vehicle ECU/TPMS so the vehicle reports accurate tire conditions to the driver. This process is needed on many other vehicle wheel events, for example, when a full different set of wheels is installed on a vehicle to replace summer tires and switched with winter tires, which is common in northern states and foreign countries. Other examples include when a single tire pressure sensor is replaced due to damage. In each instance, the TPMS needs to be updated and the ECU retrained or reprogrammed to take into account the change in wheel or wheels and the respective different TPMS wheel sensor.
In a conventional use of a TPMS tool, for example when the existing vehicle wheels are rotated in a commercial service garage as described above, the TPMS tool is sequentially brought into close proximity to the exterior of each tire. For each tire, the TPMS sends an electronic signal which is received by the adjacent sensor to activate, trigger or awaken the sensor which is in an inactive sleep mode to conserve battery power. The sensor awakens and transmits a predetermined signal or signals providing the sensor ID and other preselected information.
Depending on the type of TPMS tool, basic TPMS tools will activate the sensor to force it to transmit internal sensor information, internally process the data, and send a signal or signals to the ECU to “reset” or reprogram the ECU to account for the different location of existing sensors or new sensors. An example of such a tool is the ATEQ model VT15 manufactured by ATEQ, assignee of the present invention, and which is incorporated herein by reference. More sophisticated TPMS tools include additional features to decode the signals transmitted by the sensors to the ECU. This may include reading and displaying the information on a tool visual display for the service garage technician. This decoding may include, for example, the sensor data on tire air pressure, tire air temperature, tire rotational speed, remaining sensor battery life or condition depending on the type of sensor or TPMS tool. The TPMS tool stores the information in memory, processes the received information according to preprogrammed instructions in the tool, and transmits a signal or signals to the ECU to reprogram the ECU for the changed wheel and sensor event. An example of such a tool is the ATEQ model VT55 manufactured by ATEQ Corporation, assignee of the present invention and which is incorporated herein by reference. The decoding of information is useful as a diagnostic tool to identify the particular tire condition to better troubleshoot problems. An easy example would be to specifically identify which sensor is transmitting an alert condition or identify a sensor that has stopped working due to a dead battery or damage.